The disk just contains raw data - it has no concept of LUNs. How the data has been arranged on your disk, is entirely up to the implementation on the MD3000i appliance, which is a black box in this respect.
The MD3000i appliance probably has written the metadata about the structure and the configuration of the array to the end of the disk, that's why you seem to be able to access what you've exported as "the first lun". There is probably no safe way to tell where the "second lun" assignment starts, if it is contiguous and if it is safe to just assume that you can read the data in blocks without problems or if more metadata has been embedded in there, breaking your filesystem structures.
If you are avid for trying some data recovery on your own, you might just check out where the last partition of your "first lun" ends, use a disk editor to verify that the data area following your last partition on "first lun" contains a new partition table and copy the data off there to another disk using dd. You also might want to take a look at TestDisk - it would help you with some of the recovery tasks.
Whatever you do to the disk - at least take a full copy using "dd" or some other imaging software first. Better yet, only operate on the copy instead of the original disk. This way you would have a backup that you still could send to some data recovery service if something goes wrong with your own attempts.